Deep brain stimulation current steering with split electrodes

ABSTRACT

A device for brain stimulation includes a lead having a longitudinal surface, a proximal end, a distal end and a lead body. The device also includes a plurality of electrodes disposed along the longitudinal surface of the lead near the distal end of the lead. The plurality of electrodes includes a first set of segmented electrodes comprising at least two segmented electrodes disposed around a circumference of the lead at a first longitudinal position along the lead; and a second set of segmented electrodes comprising at least two segmented electrodes disposed around a circumference of the lead at a second longitudinal position along the lead. The device further includes one or more conductors that electrically couple together all of the segmented electrodes of the first set of segmented electrodes.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/162,348 filed Jan. 23, 2014, now U.S. Pat. No. 8,914,121, which is acontinuation of U.S. patent application Ser. No. 13/920,986 filed Jun.18, 2013, now U.S. Pat. No. 8,649,873, which is a continuation of U.S.patent application Ser. No. 12/761,622 filed Apr. 16, 2010, now U.S.Pat. No. 8,473,061, which claims the benefit of U.S. Provisional PatentApplication Ser. No. 61/170,037 filed Apr. 16, 2009, and U.S.Provisional Patent Application Ser. No. 61/316,759 filed Mar. 23, 2010,all of which are incorporated herein by reference in their entirety.

FIELD

The invention is directed to devices and methods for brain stimulationincluding deep brain stimulation. In addition, the invention is directedto devices and method for brain stimulation using a lead having aplurality of segmented electrodes.

BACKGROUND

Deep brain stimulation can be useful for treating a variety ofconditions including, for example, Parkinson's disease, dystonia,essential tremor, chronic pain, Huntington's Disease, levodopa-induceddyskinesias and rigidity, bradykinesia, epilepsy and seizures, eatingdisorders, and mood disorders. Typically, a lead with a stimulatingelectrode at or near a tip of the lead provides the stimulation totarget neurons in the brain. Magnetic resonance imaging (MRI) orcomputerized tomography (CT) scans can provide a starting point fordetermining where the stimulating electrode should be positioned toprovide the desired stimulus to the target neurons.

Upon insertion, current is introduced along the length of the lead tostimulate target neurons in the brain. This stimulation is provided byelectrodes, typically in the form of rings, disposed on the lead. Thecurrent projects from each electrode similarly and in all directions atany given length along the axis of the lead. Because of the shape of theelectrodes, radial selectivity of the current is minimal. This resultsin the unwanted stimulation of neighboring neural tissue, undesired sideeffects and an increased duration of time for the proper therapeuticeffect to be obtained.

BRIEF SUMMARY

One embodiment is a device for brain stimulation that includes a leadhaving a longitudinal surface, a proximal end, a distal end and a leadbody. The device also includes a plurality of electrodes disposed alongthe longitudinal surface of the lead near the distal end of the lead.The plurality of electrodes includes a first set of segmented electrodescomprising at least two segmented electrodes disposed around acircumference of the lead at a first longitudinal position along thelead; and a second set of segmented electrodes comprising at least twosegmented electrodes disposed around a circumference of the lead at asecond longitudinal position along the lead. The device further includesone or more conductors that electrically couple together all of thesegmented electrodes of the first set of segmented electrodes.

Another embodiment is a method for brain stimulation that includesinserting a device into a cranium of a patient. The device includes alead having a longitudinal surface, a proximal end and a distal end, anda plurality of electrodes disposed along the longitudinal surface of thelead. The plurality of electrodes includes at least one set of segmentedelectrodes where each set of segmented electrodes has a plurality ofsegmented electrodes disposed around a circumference of the lead at alongitudinal position along the lead. The method further includesselectively producing anodic and cathodic currents at the plurality ofelectrodes to stimulate a target neuron using the plurality ofelectrodes. During operation, the anodic current or cathodic current isshifted from any one of the plurality of segmented electrodes to anadjacent one of the plurality of segmented electrodes.

Yet another embodiment is a method for brain stimulation that includesinserting a device into a cranium of a patient. The device includes alead having a longitudinal surface, a proximal end and a distal end, anda plurality of electrodes disposed along the longitudinal surface of thelead. The plurality of electrodes includes at least one set of segmentedelectrodes where each set of segmented electrodes has a plurality ofsegmented electrodes disposed around a circumference of the lead at alongitudinal position along the lead. The method further includesselectively producing anodic and cathodic currents at the plurality ofelectrodes to stimulate a target neuron using the plurality ofelectrodes. A first timing channel is defined which provides a first setof stimulation pulses to any one of the plurality of segmentedelectrodes. At least one second timing channel is defined which providesat least a second set of stimulation pulses to any one of the pluralityof segmented electrodes. The first and second sets of stimulation pulsesare cycled with the first and second sets of stimulation pulsesnon-overlapping in the first and second timing channels.

A further embodiment is an implantable stimulation device for brainstimulation that includes a lead having a longitudinal surface, aproximal end and a distal end. The lead includes a plurality ofelectrodes disposed along the longitudinal surface of the lead near thedistal end of the lead. The plurality of electrodes includes i) a firstring electrode disposed at a first longitudinal position along the lead,ii) a first set of segmented electrodes comprising at least threesegmented electrodes disposed around a circumference of the lead at asecond longitudinal position along the lead, iii) a second set ofsegmented electrodes comprising at least three segmented electrodesdisposed around a circumference of the lead at a third longitudinalposition along the lead, and iv) a second ring electrode disposed at afourth longitudinal position along the lead. The second and thirdlongitudinal positions are between the first and fourth longitudinalpositions. The implantable stimulation device also includes a controlunit coupleable to the lead. The implantable stimulation device is aconstant-current, multi-channel device, with independent programmabilityof each stimulation channel to provide current steering.

In one embodiment, a device for brain stimulation includes a lead havinga longitudinal surface, a proximal end and a distal end. A plurality ofelectrodes is disposed along the longitudinal surface of the lead nearthe distal end of the lead. The plurality of electrodes includes atleast one ring electrode, and at least one set of segmented electrodes.Each set of segmented electrodes includes at least two segmentedelectrodes, which may be configured and arranged so as to collectivelyform a surface in the shape of a ring but having cutouts between them toseparate the at least two segmented electrodes.

In another embodiment, a device for brain stimulation includes a leadhaving a longitudinal surface, a proximal end and a distal end. Aplurality of electrodes is disposed along the longitudinal surface ofthe lead near the distal end of the lead. The plurality of electrodesincludes at least one ring electrode, and at least one set of segmentedelectrodes. Each set of segmented electrodes includes a plurality ofelectrodes disposed at intervals around the circumference of the lead ator near a same longitudinal position along the lead.

In yet another embodiment, a method for brain stimulation includesinserting a device into a cranium of a patient. The device includes alead having a longitudinal surface, a proximal end and a distal end. Aplurality of electrodes is disposed along the longitudinal surface ofthe lead. The plurality of electrodes includes at least one ringelectrode, and at least one set of segmented electrodes. The set ofsegmented electrodes includes at least two segmented electrodes that maybe configured and arranged so as to collectively form a surface in theshape of a ring but having cutouts between them to separate the at leasttwo segmented electrodes. Anodic and cathodic currents are selectivelyproduced at the plurality of electrodes to stimulate a target neuronusing the plurality of electrodes.

BRIEF DESCRIPTION OF THE DRAWINGS

Non-limiting and non-exhaustive embodiments of the present invention aredescribed with reference to the following drawings. In the drawings,like reference numerals refer to like parts throughout the variousfigures unless otherwise specified.

For a better understanding of the present invention, reference will bemade to the following Detailed Description, which is to be read inassociation with the accompanying drawings, wherein:

FIG. 1 is a schematic perspective view of one embodiment of a portion ofa lead having a plurality of segmented electrodes, according to theinvention;

FIG. 2 is a schematic perspective view of another embodiment of aportion of a lead having a plurality of segmented electrodes arranged ina staggered orientation, according to the invention;

FIG. 3A is a schematic perspective view of a third embodiment of aportion of a lead having a plurality of segmented electrodes, accordingto the invention;

FIG. 3B is a schematic perspective view of a fourth embodiment of aportion of a lead having a plurality of segmented electrodes, accordingto the invention;

FIG. 4 is a schematic diagram of radial current steering along variouselectrode levels along the length of a lead, according to the invention;

FIG. 5 is a schematic diagram of one embodiment of stimulation volumeusing monopolar and multipolar stimulation techniques, according to theinvention;

FIG. 6 is a schematic diagram of one embodiment of an anode and cathodecurrent shifting technique, according to the invention;

FIG. 7A is a schematic perspective view of one embodiment of a portionof a lead having a ring electrode, according to the invention;

FIG. 7B is a schematic cross-sectional view of the portion of the leadof FIG. 7A, according to the invention;

FIG. 7C is a schematic diagram of possible centroid locations of themonopolar and multipolar stimulation volume of the portion of the leadof FIG. 7A, according to the invention;

FIG. 8A is a schematic perspective view of one embodiment of a portionof a lead having sets of two segmented electrodes, according to theinvention;

FIG. 8B is a schematic cross-sectional view of the portion of the leadof FIG. 8A, according to the invention;

FIG. 8C is a schematic diagram of possible centroid locations of themonopolar and multipolar stimulation volume of the portion of the leadof FIG. 8A, according to the invention;

FIG. 9A is a schematic view of one embodiment of a portion of a leadhaving sets of three segmented electrodes, according to the invention;

FIG. 9B is a schematic cross-sectional view of the portion of the leadof FIG. 9A, according to the invention;

FIG. 9C is a schematic diagram of possible centroid locations of themonopolar and multipolar stimulation volume of the lead of FIG. 9A,according to the invention;

FIG. 10A is a schematic diagram of possible centroid locations of themonopolar and multipolar stimulation volume of a lead having sets ofthree segmented electrodes, according to the invention;

FIG. 10B is a schematic diagram of the possible centroid locations ofthe monopolar and multipolar stimulation volume of a lead having sets offour segmented electrodes, according to the invention;

FIG. 10C is a schematic diagram of possible centroid locations of themonopolar and multipolar stimulation volume of a lead having sets ofeight segmented electrodes, according to the invention;

FIG. 11A is a schematic diagram of one embodiment of an electrodestimulating a target, according to the invention;

FIG. 11B is a schematic diagram of a second embodiment of an electrodestimulating a target, according to the invention;

FIG. 11C is a schematic diagram of one embodiment of two electrodessimultaneously stimulating a target, according to the invention;

FIG. 11D is a schematic diagram of one embodiment of an electrodecycling technique, according to the invention;

FIG. 12 is a schematic side view of one embodiment of a lead and astylet, according to the invention;

FIG. 13 is a schematic side view of a portion of an embodiment of a leadwith segmented electrodes including ganged (i.e., electrically coupled)segmented electrodes, according to the invention;

FIG. 14 is a schematic cross-sectional view of a portion of anembodiment of a lead with ganged (i.e., electrically coupled)electrodes, according to the invention;

FIG. 15 is a schematic cross-sectional view of a portion of anotherembodiment of a lead with ganged (i.e., electrically coupled)electrodes, according to the invention;

FIG. 16 is a schematic cross-sectional view of a portion of a furtherembodiment of a lead with ganged (i.e., electrically coupled)electrodes, according to the invention;

FIG. 17 is a schematic cross-sectional view of a portion of yet anotherembodiment of a lead with ganged (i.e., electrically coupled)electrodes, according to the invention;

FIG. 18 is a schematic side view of a portion of another embodiment of alead with segmented electrodes including ganged (i.e., electricallycoupled) segmented electrodes, according to the invention;

FIG. 19 is a schematic side view of a portion of a further embodiment ofa lead with segmented electrodes including ganged (i.e., electricallycoupled) segmented electrodes, according to the invention;

FIG. 20 is a schematic side view of a portion of yet another embodimentof a lead with segmented electrodes including ganged (i.e., electricallycoupled) segmented electrodes, according to the invention;

FIG. 21 is a schematic side view of a portion of an embodiment of a leadwith segmented electrodes, according to the invention;

FIG. 22 is a schematic side view of a portion of another embodiment of alead with segmented electrodes, according to the invention;

FIG. 23 is a schematic side view of a portion of a further embodiment ofa lead with segmented electrodes, according to the invention;

FIG. 24 is a schematic side view of a portion of an embodiment of a leadwith segmented electrodes and a tip electrode, according to theinvention;

FIG. 25 is a schematic side view of a portion of another embodiment of alead with segmented electrodes and a tip electrode, according to theinvention;

FIG. 26 is a schematic side view of a portion of an embodiment of a leadwith segmented electrodes and a microelectrode, according to theinvention;

FIG. 27 is a schematic side view of a portion of an embodiment of a leadwith segmented electrodes and microelectrodes, according to theinvention;

FIG. 28 is a schematic side view of a portion of another embodiment of alead with segmented electrodes and microelectrodes, according to theinvention; and

FIG. 29 is a schematic side view of a portion of a further embodiment ofa lead with segmented electrodes including ganged (i.e., electricallycoupled) segmented electrodes, according to the invention.

DETAILED DESCRIPTION

The present invention is directed to the area of devices and methods forbrain stimulation including deep brain stimulation. In addition, theinvention is directed to devices and method for brain stimulation usinga lead having a plurality of segmented electrodes.

A lead for deep brain stimulation may include stimulation electrodes,recording electrodes, or a combination of both. A practitioner maydetermine the position of the target neurons using the recordingelectrode(s) and then position the stimulation electrode(s) accordinglywithout removal of a recording lead and insertion of a stimulation lead.In some embodiments, the same electrodes can be used for both recordingand stimulation. In some embodiments, separate leads can be used; onewith recording electrodes which identify target neurons, and a secondlead with stimulation electrodes that replaces the first after targetneuron identification. A lead may include recording electrodes spacedaround the circumference of the lead to more precisely determine theposition of the target neurons. In at least some embodiments, the leadis rotatable so that the stimulation electrodes can be aligned with thetarget neurons after the neurons have been located using the recordingelectrodes.

Deep brain stimulation devices and leads are described in the art. See,for instance, U.S. Patent Publication 2006/0149335 A1 (“Devices andMethods For Brain Stimulation”), and co-pending patent application U.S.Ser. No. 12/237,888 (“Leads With Non-Circular-Shaped Distal Ends ForBrain Stimulation Systems and Methods of Making and Using”). Each ofthese references is incorporated herein by reference in its respectiveentirety.

FIG. 12 illustrates one embodiment of a device 1200 for brainstimulation. The device includes a lead 100, ring electrodes 120,segmented electrodes 130, a connector 1230 for connection of theelectrodes to a control unit, and a stylet 1260 for assisting ininsertion and positioning of the lead in the patient's brain. The stylet1260 can be made of a rigid material. Examples of suitable materialsinclude tungsten, stainless steel, or plastic. The stylet 1260 may havea handle 1270 to assist insertion into the lead, as well as rotation ofthe stylet and lead. The connector 1230 fits over the proximal end ofthe lead 100, preferably after removal of the stylet 1260.

In one example of operation, access to the desired position in the braincan be accomplished by drilling a hole in the patient's skull or craniumwith a cranial drill (commonly referred to as a burr), and coagulatingand incising the dura mater, or brain covering. The lead 100 can beinserted into the cranium and brain tissue with the assistance of thestylet 1260. The lead can be guided to the target location within thebrain using, for example, a stereotactic frame and a microdrive motorsystem. In some embodiments, the microdrive motor system can be fully orpartially automatic. The microdrive motor system may be configured toperform one or more the following actions (alone or in combination):rotate the lead, insert the lead, or retract the lead. In someembodiments, measurement devices coupled to the muscles or other tissuesstimulated by the target neurons or a unit responsive to the patient orclinician can be coupled to the control unit or microdrive motor system.The measurement device, user, or clinician can indicate a response bythe target muscles or other tissues to the stimulation or recordingelectrode(s) to further identify the target neurons and facilitatepositioning of the stimulation electrode(s). For example, if the targetneurons are directed to a muscle experiencing tremors, a measurementdevice can be used to observe the muscle and indicate changes in tremorfrequency or amplitude in response to stimulation of neurons.Alternatively, the patient or clinician may observe the muscle andprovide feedback.

The lead 100 for deep brain stimulation can include stimulationelectrodes, recording electrodes, or both. In at least some embodiments,the lead is rotatable so that the stimulation electrodes can be alignedwith the target neurons after the neurons have been located using therecording electrodes.

Stimulation electrodes may be disposed on the circumference of the leadto stimulate the target neurons. Stimulation electrodes may bering-shaped so that current projects from each electrode equally inevery direction at any given length along the axis of the lead. Toenhance current steering, segmented electrodes can be utilizedadditionally or alternatively. Though the following descriptiondiscusses stimulation electrodes, it will be understood that allconfigurations of the stimulation electrodes discussed may be utilizedin arranging recording electrodes as well.

FIG. 1 illustrates one embodiment of a lead 100 for brain stimulation.The device includes a lead body 110, one or more ring electrodes 120,and a plurality of segmented electrodes 130. The lead body 110 can beformed of a biocompatible, non-conducting material such as, for example,a polymeric material. Suitable polymeric materials include, but are notlimited to, silicone, polyethylene, polyurethanes, polyureas, orpolyurethane-ureas. In at least some instances, the lead may be incontact with body tissue for extended periods of time. In at least someembodiments, the lead has a cross-sectional diameter of no more than 1.5mm and may be in the range of 0.75 to 1.5 mm in at least someembodiments, the lead has a length of at least 10 cm and the length ofthe lead may be in the range of 25 to 70 cm.

Stimulation electrodes may be disposed on the lead body 110. Thesestimulation electrodes may be made using a metal, alloy, conductiveoxide, or any other suitable conductive material. Examples of suitablematerials include, but are not limited to, platinum, iridium, platinumiridium alloy, stainless steel, titanium, or tungsten. Preferably, thestimulation electrodes are made of a material that is biocompatible anddoes not substantially corrode under expected operating conditions inthe operating environment for the expected duration of use.

In at least some embodiments, any of the electrodes can be used as ananode or cathode and carry anodic or cathodic current. In someinstances, an electrode might be an anode for a period of time and acathode for a period of time. In other embodiments, the identity of aparticular electrode or electrodes as an anode or cathode might befixed.

Stimulation electrodes in the form of ring electrodes 120 may bedisposed on any part of the lead body 110, usually near a distal end ofthe lead. FIG. 1 illustrates a portion of a lead having two ringelectrodes. Any number of ring electrodes, or even a single ringelectrode, may be disposed along the length of the lead body 110. Forexample, the lead body may have one ring electrode, two ring electrodes,three ring electrodes or four ring electrodes. In some embodiments, thelead will have five, six, seven or eight ring electrodes. It will beunderstood that any number of ring electrodes may be disposed along thelength of the lead body 110. In some embodiments, the ring electrodes120 are substantially cylindrical and wrap around the entirecircumference of the lead body 110. In some embodiments, the outerdiameter of the ring electrodes 120 is substantially equal to the outerdiameter of the lead body 110. The width of ring electrodes 120 may varyaccording to the desired treatment and the location of the targetneurons. In some embodiments the width of the ring electrode 120 is lessthan or equal to the diameter of the ring electrode 120. In otherembodiments, the width of the ring electrode 120 is greater than thediameter of the ring electrode 120.

In at least some embodiments, the lead also contains a plurality ofsegmented electrodes 130. Any number of segmented electrodes 130 may bedisposed on the lead body 110. In some embodiments, the segmentedelectrodes 130 are grouped in sets of segmented electrodes, each setdisposed around the circumference of the lead at or near a particularlongitudinal position. The lead may have any number of sets of segmentedelectrodes. In at least some embodiments, the lead has one, two, three,four, five, six, seven, or eight sets of segmented electrodes. In atleast some embodiments, each set of segmented electrodes contains thesame number of segmented electrodes 130. In some embodiments, each setof segmented electrodes contains three segmented electrodes 130. In atleast some other embodiments, each set of segmented electrodes containstwo, four, five, six, seven or eight segmented electrodes. The segmentedelectrodes 130 may vary in size and shape. In some embodiments, thesegmented electrodes 130 are all of the same size, shape, diameter,width or area or any combination thereof. In some embodiments, thesegmented electrodes of each set (or even all segmented electrodes) maybe identical in size and shape.

In at least some embodiments, each set of segmented electrodes 130 maybe disposed around the circumference of the lead body 110 to form asubstantially or approximately cylindrical shape or ring around the leadbody 110. The spacing of the segmented electrodes 130 around thecircumference of the lead body 110 may vary as will be described withreference to FIGS. 7B, 8B and 9B. In at least some embodiments, equalspaces, gaps or cutouts are disposed between each segmented electrodes130 around the circumference of the lead body 110. In other embodiments,the spaces, gaps or cutouts between segmented electrodes may differ insize or shape. In other embodiments, the spaces, gaps, or cutoutsbetween segmented electrodes may be uniform for a particular set ofsegmented electrodes or for all sets of segmented electrodes. Thesegmented electrodes 130 may be positioned in irregular or regularintervals around the lead body 110.

Conductors (not shown) that attach to or from the ring electrodes 120and segmented electrodes 130 also pass through the lead body 110. Theseconductors may pass through the material of the lead or through a lumendefined by the lead. The conductors are presented at a connector forcoupling of the electrodes to a control unit (not shown), generally anmulti-channel implantable pulse generator (IPG) having at least twoindependently controllable channels that deliver stimulus pulses thatare programmable for current amplitude, pulsewidth and frequency ofstimulus. Each channel is independently programmable so that one channelmay act as a cathode and the other an anode in a bipolar stimulationmode, or only one channel acts as cathode while the housing of the IPGacts as an anode, or both channels deliver cathodic current while thehousing of the implantable pulse generator acts as a return anode, orone channel may act as cathode while both the other channel and thehousing of the IPG act as anode, or similar combinations of oppositepolarity. More commonly the IPG can have 8, 16 or 32 independentlyprogrammable channels, wherein each channel can be independently (a)turned off, (b) be on as cathode or (c) be on as anode, at any oneinstant in time. Because each channel is fully independently functioningand programmable, there are many possible monopolar combinations (wherethe IPG housing is an anode electrode) and bipolar, multi-polarcombinations (where the IPG housing is not an anode electrode). In anIPG with four independently programmable channel a, b, c and d, eachchannel coupled separately four electrode segments of a segmented lead,there are the following monopolar combinations, a, b, c, d, ab, ac, ad,abc, abd, acd, be, bd, cd, bed, and abed with the IPG housing as theanode. As one example, for abd, a possible programming is: a=1 milliampscurrent pulse, b=1.5 milliamps current pulse and c=1.25 current pulse,simultaneously delivered. The IPG housing sources 3.75 milliamps ofcurrent. When the IPG housing is off, then the possible combinations areab, ac, ad, abc, abd, acd, be, bd, cd, bed, and abed where at least oneelectrode in combination is functioning in one instant in time as ananode (+) return electrode and at least one electrode in the combinationis functioning as a cathode (−). As an example, in the combination bed,a possible way to program is: b=1 milliamps cathodic current, c=2.25milliamps anodic current and d=1.25 milliamps cathodic current. Notethat each channel can sink cathodic current or source anodic current,and each channel can have different amplitudes. This is what is meant bya multi-channel IPG having fully independently programmable,constant-current, channels. In one embodiment, the stimulationelectrodes correspond to wire conductors that extend out of the leadbody 110 and are then trimmed or ground down flush with the leadsurface. The conductors may be coupled to a control unit to providestimulation signals, often in the form of pulses, to the stimulationelectrodes.

FIG. 2 is a schematic perspective view of another embodiment of a leadhaving a plurality of segmented electrodes. As seen in FIG. 2, theplurality of segmented electrodes 130 may be arranged in differentorientations relative to each other. In contrast to FIG. 1, where thetwo sets of segmented electrodes are aligned along the length of thelead body 110, FIG. 2 displays another embodiment in which the two setsof segmented electrodes 130 are staggered. In at least some embodiments,the sets of segmented electrodes are staggered such that no segmentedelectrodes are aligned along the length of the lead body 110. In someembodiments, the segmented electrodes may be staggered so that at leastone of the segmented electrodes is aligned with another segmentedelectrode of a different set, and the other segmented electrodes are notaligned.

Any number of segmented electrodes 130 may be disposed on the lead body110 in any number of sets. FIGS. 1 and 2 illustrate embodimentsincluding two sets of segmented electrodes. These two sets of segmentedelectrodes 130 may be disposed in different configurations. FIG. 3A is aschematic perspective view of a third embodiment of a lead having aplurality of segmented electrodes. The lead body 110 of FIG. 3A has aproximal end and a distal end. As will be appreciated from FIG. 3A, thetwo sets of segmented electrodes 130 are disposed on the distal end ofthe lead body 110, distal to the two ring electrodes 120. FIG. 3B is aschematic perspective view of a fourth embodiment of a lead body 110. InFIG. 3B, the two sets of segmented electrodes 130 are disposed proximalto the two ring electrodes 120. By varying the location of the segmentedelectrodes 130, different coverage of the target neurons may beselected. For example, the electrode arrangement of FIG. 3A may beuseful if the physician anticipates that the neural target will becloser to the distal tip of the lead body 110, while the electrodearrangement of FIG. 3B may be useful if the physician anticipates thatthe neural target will be closer to the proximal end of the lead body110. In at least some embodiments, the ring electrodes 120 alternatewith sets of segmented electrodes 130.

Any combination of ring electrodes 120 and segmented electrodes 130 maybe disposed on the lead. In some embodiments the segmented electrodesare arranged in sets. For example, a lead may include a first ringelectrode 120, two sets of segmented electrodes, each set formed ofthree segmented electrodes 130, and a final ring electrode 120 at theend of the lead. This configuration may simply be referred to as a1-3-3-1 configuration. It may be useful to refer to the electrodes withthis shorthand notation. Thus, the embodiment of FIG. 3A may be referredto as a 1-1-3-3 configuration, while the embodiment of FIG. 3B may bereferred to as a 3-3-1-1 configuration. Other eight electrodeconfigurations include, for example, a 2-2-2-2 configuration, where foursets of segmented electrodes are disposed on the lead, and a 4-4configuration, where two sets of segmented electrodes, each having foursegmented electrodes 130 are disposed on the lead. In some embodiments,the lead will have 16 electrodes. Possible configurations for a16-electrode lead include, but are not limited to 4-4-4-4, 8-8,3-3-3-3-3-1 (and all rearrangements of this configuration), and2-2-2-2-2-2-2-2.

FIG. 4 is a schematic diagram to illustrate radial current steeringalong various electrode levels along the length of a lead. Whileconventional lead configurations with ring electrodes are only able tosteer current along the length of the lead (the z-axis), the segmentedelectrode configuration is capable of steering current in the x-axis,y-axis as well as the z-axis. Thus, the centroid of stimulation may besteered in any direction in the three-dimensional space surrounding thelead body 110. In some embodiments, the radial distance, r, and theangle θ around the circumference of the lead body 110 may be dictated bythe percentage of anodic current (recognizing that stimulationpredominantly occurs near the cathode, although strong anodes may causestimulation as well) introduced to each electrode as will be describedin greater detail below. In at least some embodiments, the configurationof anodes and cathodes along the segmented electrodes 130 allows thecentroid of stimulation to be shifted to a variety of differentlocations along the lead body 110.

As can be appreciated from FIG. 4, the centroid of stimulation can beshifted at each level along the length of the lead. The use of multiplesets of segmented electrodes 130 at different levels along the length ofthe lead allows for three-dimensional current steering. In someembodiments, the sets of segmented electrodes 130 are shiftedcollectively (i.e. the centroid of simulation is similar at each levelalong the length of the lead). In at least some other embodiments, eachset of segmented electrodes 130 is controlled independently. Each set ofsegmented electrodes may contain two, three, four, five, six, seven,eight or more segmented electrodes. It will be understood that differentstimulation profiles may be produced by varying the number of segmentedelectrodes at each level. For example, when each set of segmentedelectrodes includes only two segmented electrodes, uniformly distributedgaps (inability to stimulate selectively) may be formed in thestimulation profile. In some embodiments, at least three segmentedelectrodes 130 are utilized to allow for true 360° selectivity. Thisconcept will be further explained below with reference to FIGS. 8A-C and9A-9C.

Any type of stimulation technique can be used including monopolarstimulation techniques, bipolar stimulation techniques, and multipolarstimulation techniques. FIG. 5 is a schematic diagram of stimulationvolume using monopolar and multipolar stimulation techniques. Inmonopolar stimulation techniques, all local electrodes are of the samepolarity (i.e., an electrode of a different polarity is positioned faraway, e.g., on the housing of the IPG, and does not substantially affectthe stimulation field and centroid. Therefore, the stimulation centroidstays close to the stimulation electrode 131 as represented by B in FIG.5. However, in multipolar stimulation, local anode(s) and cathode(s) areused. Therefore, the stimulation field is “driven away” from theelectrodes, pushing out the stimulation centroid along the radius r. Thecentroid of the multipolar stimulation field is represented by A. Notethat stimulation amplitude may need to be increased when switching frommonopolar to multipolar to keep the same activation volume. As seen inFIG. 5, the stimulation volume varies between monopolar stimulation,represented by dashed lines, and multipolar stimulation, represented bysolid lines. The centroid of the stimulation volume moves out along rwhen stimulation is changed from monopolar to multipolar. In FIG. 5, thefirst segmented electrode 131 is used as the cathode and the secondsegmented electrodes 132 and 133 are used as anodes in the multipolarconfiguration, although any other configuration of anode and cathode ispossible. Nerve fibers considered were perpendicular to the lead for thepurpose of estimating the region of activation. It is recognized thatcathodes, and more particularly anodes, may have a stimulating effectfor other fiber orientations.

In at least some embodiments, the shift from monopolar stimulation tomultipolar stimulation is incremental. For example, a device may startwith a cathode (e.g. electrode 131) on the lead and 100% of the anode onthe case of the device, or some other nonlocal location. The anode maythen be incrementally moved to one or more of the local segmentedelectrodes 130. Any incremental shift can be used or the shift may evenbe continuous over a period of time. In some embodiments, the shift isperformed in 10% increments. In some other embodiments, the shift isperformed in 1%, 2%, 5%, 20%, 25%, or 50% increments. As the anode isincrementally moved from the case to one or more of the segmentedelectrodes 130, the centroid incrementally moves in the radialdirection, r. Table A, below, illustrates an anode shift from a case toone segmented electrode at 10% increments:

TABLE A Electrode Non-Local Anode 0 100 10 90 20 80 30 70 40 60 50 50 6040 70 30 80 20 90 10 100 0Similarly, Table B, below, illustrates an anodic shift from a non-localanode of the device to two segmented electrodes on the lead:

TABLE B Electrode 1 Electrode 2 Non-Local Anode 0 0 100 10 10 80 20 2060 30 30 40 40 40 20 50 50 0In some embodiments, as in Table B, the two segmented electrodes equallysplit the anode. In other embodiments, the two segmented electrodesunequally split the anode. The two segmented electrodes may also splitthe anode in any ratio, such as 1.5:1, 2:1 or 3:1.

Another stimulation technique is a method that can be called “chasingthe cathode” and can be utilized to project the centroid of thestimulation volume. In this method, the anode chases the cathode aroundthe circumference of the lead body 110 (i.e., as θ changes). It will berecognized that another embodiment can have the cathode chase the anode.After the cathodic current has incrementally shifted to the nextsegmented electrode, the anodic current begins to incrementally shift toanother of the segmented electrodes, for a set of three segmentedelectrodes, the shift is to the previously cathodic segmented electrode.Once the anode has completely shifted, the present cathode begins toincrementally shift to the next segmented electrode, and the cyclecontinues. In at least some embodiments, three or more segmentedelectrodes are utilized for chasing the cathode. In some cases, theanode shifts may be larger (e.g., 20%) than the cathode shifts (e.g.,10%) or vice versa. FIG. 6 is a schematic diagram of the “chasing thecathode” technique. Each segmented electrode 131-133 of FIG. 6 islabeled with the relevant percentage of the local cathode, designatedwith (−), or local anode, designated with (+). For example, in the firststep labeled “1”, the first segmented electrode 130 is labeled 100,because that segmented electrode carries 100% of the local anode. Evenif the 70% of the anode is on a the first segmented electrode 131 and30% of the anode is on the case, the first segmented electrode 131 willbe labeled as 100, because that electrode carries 100% of the localanode, even though it carries 70% of the system anode.

As seen in FIG. 6, the device begins with 100 on the first segmentedelectrode 131, −100 on the second segmented electrode 132 and 0 on thethird segmented electrode 133. At a later point, the first segmentedelectrode 131 is shown at 100, the second segmented electrode 132 isshown at −50, and the third segmented electrode 133 is shown at −50.This incremental shift may be iterated until the device returns to thefirst state where the configuration is 100 on the first segmentedelectrode 131, −100 on the second segmented electrode 132 and 0 on thethird segmented electrode 133. Table C, below, shows one cycle of the“current chasing” technique, where the anodic and cathodic shifts areperformed at 10% increments.

TABLE C Electrode 1 Electrode 2 Electrode 3 1. 100 −100 0 2. 100 −90 −103. 100 −80 −20 4. 100 −70 −30 5. 100 −60 −40 6. 100 −50 −50 7. 100 −40−60 8. 100 −30 −70 9. 100 −20 −80 10. 100 −10 −90 11. 100 0 −100 12. 9010 −100 13. 80 20 −100 14. 70 30 −100 15. 60 40 −100 16. 50 50 −100 17.40 60 −100 18. 30 70 −100 19. 20 80 −100 20. 10 90 −100 21. 0 100 −10022. −10 100 −90 23. −20 100 −80 24. −30 100 −70 25. −40 100 −60 26. −50100 −50 27. −60 100 −40 28. −70 100 −30 29. −80 100 −20 30. −90 100 −1031. −100 100 0 32. −100 90 10 33. −100 80 20 34. −100 70 30 35. −100 6040 36. −100 50 50 37. −100 40 60 38. −100 30 70 39. −100 20 80 40. −10010 90 41. −100 0 100 42. −90 −10 100 43. −80 −20 100 44. −70 −30 100 45.−60 −40 100 46. −50 −50 100 47. −40 −60 100 48. −30 −70 100 49. −20 −80100 50. −10 −90 100 51. 0 −100 100 52. 10 −100 90 54. 30 −100 70 55. 40−100 60 56. 50 −100 50 57. 60 −100 40 58. 70 −100 30 59. 80 −100 20 60.90 −100 10 61. 100 −100 0

In some embodiments, the anode is located only on the case. In someother embodiments, the anode is partially located on the case and one ormore electrodes. As previously indicated, the data in FIG. 6 and Table Cindicates only the local percentages of the anode and the cathode. Thus,even though a segmented electrodes is labeled with 100, i.e. that itcarries 100% of the local anode, it may carry anywhere between 1% to100% of the total system anodic current. The same is true for cathodiccurrent such that at any row, the local cathodic current may be anywherebetween 1% to 100% of the system cathodic current, even though it islabeled as 100.

A multi-channel set up technique may also be used to shift current fromone electrode to another. For example, the use of two timing channelsallows two potentially-viable sets of stimulation parameters to beapplied to the patient during set up in an interleaved fashion. Soapplied, the patient will independently feel the effects of the settingsof both timing channels, but in a manner that does not blur the effectof two. Thus, field shifting in this manner may reduce or eliminateintermediate states that reduce the efficacy of the therapy.

This type of field shifting will be referred to as interleaved fieldshifting and will be described with reference to Table D, below:

TABLE D Electrode 1 Electrode 2 Electrode 3 Electrode 4 Channel A 50−100 50 0 Channel B 0 0 0 0 Step 1 Channel A 50 −100 50 0 Channel B 0 25−50 25 Step 2 Channel A 50 −100 50 0 Channel B 0 50 −100 50 Step 3Channel A 50 −100 50 0 Channel B 0 50 −100 50 Step 4 Channel A 25 −50 250 Channel B 0 50 −100 50

As shown in Table D, two channels, Channel A and Channel B, are used toshift the current. In timing Channel A, the initial conditions ofelectrodes 1-4 are 50% on the first, −100% on the second, and 50% on thethird. There is no current on the fourth electrode in timing Channel Aat this initial condition. However, if the user desires to shift currentto the fourth electrode then two timing channels may be used toaccomplish this task. The user may begin by using a controller to shiftcurrent to timing Channel B.

Thus, in a first step the current associated with timing Channel A willremain constant, while timing Channel B will shift to a state having 25%on the second electrode, −50% on the third electrode and 25% on thefourth electrode. Notice that at this first step, establishment ofcurrent in timing Channel B does not immediately affect the amount ofcurrent in the initial conditions of timing Channel A as described inthe embodiment of Table C.

In a second step, the current directed to timing Channel B may again beincreased by the same amount, although the shifts need not beincremental. As can be appreciated from Table D, after the second step,the current in timing Channel B now matches that of timing Channel A,but is shifted over by one electrode. Subsequent steps are then appliedto incrementally remove the current from the initial conditionelectrodes in timing Channel A, which eventually leaves as active onlythe final condition electrodes in timing Channel B. At this point,timing Channel B is the only currently active timing channel withsegmented electrodes 2-4 having the state of the initial segmentedelectrodes 1-3.

As can be appreciated from Table D, movement from the initial conditionsto the final conditions is accomplished without the intermediary stepsduring which the electrodes are really not indicative of either theinitial or final conditions. Thus, useful stimulation may be optimizedand unnecessary side effects reduced.

FIG. 7A is a schematic view of a lead having ring electrodes 120. Thering electrodes 120 completely encircle the circumference of the leadbody 110. FIG. 7B is a schematic cross-sectional view of the lead ofFIG. 7A, showing the ring electrodes 120 encircling the lead body 110.Any number of ring electrodes 120 may be disposed on the lead body 110.In some embodiments, where only ring electrodes 120 are disposed on thelead body 110, the centroid of stimulation can only be located at asingle point within a specified plane normal to L, the length of thelead, as illustrated in FIG. 7C.

FIG. 8A is a schematic view of the lead having three sets of segmentedelectrodes, each set having two segmented electrodes 130. As illustratedin FIG. 8B, in some embodiments, two 45° cutouts are formed between thetwo segmented electrodes 130, with each segmented electrode 130 beingformed of a 135° segment. It will be recognized that the size and shapeof the segmented electrodes and cutouts can be varied. The two segmentedelectrodes 130 may be formed to cover any portion of the lead and thecutouts may be arranged to be of any distance. For example, eachsegmented electrode 130 may be formed of a 75°, 90° or 120° segment. Insome embodiments, each cutout is of the same size. In other embodiments,the two cutouts are of different sizes. By adding an additionalelectrode, or electrode segment, multipolar stimulation techniques arepossible. FIG. 8C is a schematic representation of the monopolar andmultipolar stimulation of the lead of FIG. 8A. As seen in FIG. 8C, thecentroid of the monopolar stimulation of the two electrode segments is astraight line within a specified plane normal to L. In embodimentsutilizing multipolar stimulation, the centroid of stimulation may belocated similar to that of monopolar stimulation but with an increasedrange, due to the anode driving out the centroid.

FIG. 9A is a schematic view of a lead having three sets of segmentedelectrodes, each circumferential set having three segmented electrodes130. It will be recognized that the size and shape of the segmentedelectrodes and cutouts (or space between the segmented electrodes in thecircumferential set) can be varied. As described above, each of thethree segmented electrodes 130 may be formed of segments of differentlengths. As illustrated in FIG. 9B, the segmented electrodes of FIG. 9Amay be formed of 90° segments, separated by 30° cutouts or gaps. In someother embodiments, the segments cover only 45°, 60° or 75°. In at leastsome embodiments, the cutouts (or space between segments in a set) areof different lengths. FIG. 9C is a schematic representation of themonopolar and multipolar stimulation of the lead of FIG. 9A. As seen inFIG. 9C, the addition of a third segmented electrode greatly increasesthe possibilities for stimulation. With a set of three segmentedelectrodes 130 and using only monopolar stimulation, the centroid ofstimulation may be located anywhere in a triangular space within aspecified plane normal to L, the length of the lead. With multipolarstimulation, the centroid of stimulation may be located in an increasedrange within a triangular space within a specified plane normal to L.Thus, multipolar stimulation may be used in all embodiments having morethan two segmented electrodes 130 to drive out the centroid and allowfor extended stimulation coverage. Because each electrode segment may beindependently programmed for different current amplitude and,furthermore, as cathode, anode or off, at any instant in time, thestimulation field can be tremendously varied around the circumferenceand length L of the lead. Independent current control of eachstimulation channel permits radial current steering, (i.e., where atleast two electrodes, placed closely together, deliver simultaneousstimulus pulses, having same or different current amplitudes, andeffectively place the centroid of stimulus at an angular positionbetween the two electrodes.) The same principle applies with three ormore electrodes that deliver independent constant current stimuluspulses. In effect, it permits the creation of virtual electrodes betweentwo real electrodes or complex stimulus current gradients around threeor more electrodes. This is known as “current steering”.

FIGS. 10A, 10B, and 10C are schematic representations of the monopolarand multipolar stimulation of a lead using three, four and eightsegmented electrodes. A comparison between the stimulation for monopolarand multipolar stimulation may be appreciated with reference to FIGS.10A, 10B, and 10C. For example, as previously described, when threesegmented electrodes are disposed around the circumference of the lead,the centroid of stimulation may be located anywhere in a triangularspace within a specified plane normal to L, the length of the lead.Embodiments utilizing multipolar stimulation techniques using these samesegmented electrodes allow for extended stimulation coverage andprojecting of the centroid of stimulation.

FIG. 10B illustrates the monopolar and multipolar stimulation of a leadhaving four segmented electrodes. With four segmented electrodes at eachlevel, an 8-electrode lead design may be formed. In at least someembodiments, four segmented electrodes are disposed on a lead having twoother sets of segmented electrodes, each set having two segmentedelectrodes. With four segmented electrodes, the centroid of stimulationmay be located anywhere in a square space within a specified planenormal to L, the length of the lead. As with the three segmentedelectrode configuration, a multipolar configuration can project thecentroid so that the centroid of stimulation may be located anywhere ina larger square space within a specified plane normal to L.

FIG. 10C illustrates the monopolar and multipolar stimulation of a leadhaving eight segmented electrodes at a given level. With eight segmentedelectrodes at each level, a 16-electrode lead design may be formed. Inat least some embodiments, eight segmented electrodes are disposed on alead having any other number of segmented electrodes. For example, insome embodiments, the lead will have eight segmented electrodes at onelevel, and two other sets of four segmented electrodes, one at eachlevel. As seen in FIG. 10C, with eight segmented electrodes, thecentroid of stimulation may be located anywhere in an octagonal steeringspace within a specified plane normal to L, the length of the lead. Aswith other configurations, a multipolar configuration will drive out thecentroid so that the centroid of stimulation may be located anywhere ina larger octagonal steering space within a specified plane normal to L.

In some embodiments, the device may be coupled to an implantable pulsegenerator. The implantable pulse generator may contain multiple currentsources. For example, the implantable pulse generator may contain adistinct current source for each stimulation electrode. In someembodiments, the implantable pulse generator contains multiple voltagesources.

In at least some embodiments, a cycling technique may also be used toprogram the device with greater specificity. The cycling technique mayinclude, for example, repeatedly shifting the stimulation from one areato another. Each area may define a set of stimulation parameters,including but not limited to one or more of electrode configuration,amplitude, pulse width, or current distribution. Cycling techniques maybe used to expand the total area of stimulation by, for example, placingthe centroid of stimulation effectively somewhere between the positionof the two electrodes by rapidly alternating or cycling between each oftwo electrodes. For example, suppose there are two electrodes A and B.Electrode A delivers pulses of 1.5 milliamps whereas Electrode Bdelivers 1.1 milliamps. The delivery of the stimulus pulses are rapidlyalternated between Electrode A and Electrode B, doubling the frequencyof stimulus in the overlap area, effectively emulating a virtualelectrode between Electrodes A and B. The virtual electrode ispositioned closer to Electrode B. This rapid cycling is yet another wayto achieve a region of high rate stimulation between two electrodes. Toeffect such rapid cycling, the IPG must be capable of rapidly cyclingbetween stimulation channels, or stimulate out of phase betweenstimulation channels. Or, if the electrodes are placed far enough awayfrom each other, and the current fields do not substantially overlap,the two electrodes can be used to stimulate two targetspseudo-simultaneously. Cycling techniques may also be used to eliminatestimulation of unwanted neural tissue, reduce side effects, and give theuser increased programming specificity.

Cycling techniques used for eliminating stimulation of unwanted neuraltissue will be discussed with respect to FIGS. 11A-11D. In at least someembodiments, stimulation produces a therapeutic effect at frequenciesabove 130 Hz. Therefore, target areas are often stimulated with pulsesabove 130 Hz. However, often more neural tissue is stimulated thannecessary. As shown in FIGS. 11A and 11B, the target, denoted by a blackdot, is located between two of the segmented electrodes. Using eithersegmented electrode effectively stimulates the target as shown in FIGS.11A and 11B. However, as evident from these figures, a large amount ofunnecessary tissue may be stimulated. FIG. 11C illustrates a method inwhich both segmented electrodes are employed to stimulate the target.When both electrodes are used, the target is still effectivelystimulated, but an increased area of neural tissue is unnecessarilystimulated. FIG. 11D illustrates a method in which both segmentedelectrodes are employed to stimulate the target, each segmentedelectrode stimulating at only half the original frequency. Inembodiments where each segmented electrode intermittently stimulateswith half the original frequency, the overlapping area is stimulatedwith the original frequency. Thus, the overlapping area may beeffectively stimulated at therapeutic frequencies and thenon-overlapping areas, the area enclosed within a dashed line, are notstimulated at the therapeutic frequency because they are stimulated at areduced frequency. Thus, in some embodiments, the cycling technique maybe used to refine the area of tissue stimulated at a therapeuticfrequency.

The introduction of a plurality of segmented electrodes may also be usedwith a technique which can be called “search light” programming. In someembodiments, the stimulation volume may act like the beam of light froma lighthouse. The “beam” of electrical stimulation may be swept aroundthe lead similar to how a beam of light is swept around a lighthouse orsearch light. Because multiple levels of electrodes are introduced alongthe length of the lead, the beam of electrical stimulation may also moveup and down along the lead axis in addition to rotating around thecircumference of the lead.

The system may utilize various electrodes and the methods describedabove, such as cathode and anode shifting to swing the beam orelectrical activation around and up and down the longitudinal axis ofthe lead. In some embodiments, sweeping the beam of electricalstimulation aids in optimizing therapeutic benefits. In some otherembodiments, the sweeping of the electrical stimulation is useful inselecting programs of stimulation parameters. In some embodiments, thephysician may swing the beam of electrical stimulation to one area, thenanother, and then another to optimize the therapy and/or to determinethe best target. In some other embodiments, the physician may programthe system to swing back and forth between two or more targets or areasin a cyclical manner. In at least some other embodiments, the patientmay swing the beam of electrical stimulation around until their symptomsare reduced and/or until therapy is complete. In yet another example, acomputer system may collect various inputs while automatically sweepingthe beam of electrical activation to optimize the therapy and/or todetermine the best target.

As previously indicated, the foregoing configurations may also be usedwhile utilizing recording electrodes. In some embodiments, measurementdevices coupled to the muscles or other tissues stimulated by the targetneurons or a unit responsive to the patient or clinician can be coupledto the control unit or microdrive motor system. The measurement device,user, or clinician can indicate a response by the target muscles orother tissues to the stimulation or recording electrodes to furtheridentify the target neurons and facilitate positioning of thestimulation electrodes. For example, if the target neurons are directedto a muscle experiencing tremors, a measurement device can be used toobserve the muscle and indicate changes in tremor frequency or amplitudein response to stimulation of neurons. Alternatively, the patient orclinician may observe the muscle and provide feedback.

There are many additional electrode arrangements that can be devised.FIG. 13 is a schematic side view of a distal end of one embodiment of alead 1300 with, starting from the distal end of the lead, a group of twosegmented electrodes 1302, two groups of three segmented electrodes 1304each, and another group of two segmented electrodes 1306. In thisembodiment, the group of two segmented electrodes 1302 are gangedtogether (i.e., electrically coupled together) as schematicallyindicated by line 1308. In addition, the group of two segmentedelectrodes 1306 are also ganged together as schematically indicated byline 1310.

FIG. 14 schematically illustrates one arrangement for ganging twoelectrodes together which includes coupling the two electrodes 1402using a conductor 1408 that passes through the lead body 1412. Thisconductor 1408 can be coupled to a conductor (not shown) that passesthrough the lead body to the proximal end of the lead to provide forconnection to the control unit. Alternatively, one of the electrodes1402 is electrically coupled to a conductor (not shown) that passesthrough the lead body to the proximal end of the lead to provide forconnection to the control unit or implantable pulse generator (IPG) withindependently controllable, constant-current stimulation channels andthe other electrode is coupled to the first electrode by the conductor1408. FIG. 15 schematically illustrates a similar arrangement forelectrically coupling three electrodes 1502 using conductors 1508.

FIG. 16 schematically illustrates another arrangement of two segmentedelectrodes 1602 that are coupled by a conductor 1608 that is covered byinsulating material 1614 that is preferably part of, or becomes part of,the lead body 1612. This conductor 1608 might be a wire or may be athin, flat conductor or some other connecting conductor. FIG. 17schematically illustrates yet another arrangement with two electrodes1702 and a conductor 1708. In this particular arrangement, the lead body1712 defines a lumen 1716 (e.g., a stylet lumen) and the conductor is1708 arranged around the lumen.

FIG. 18 schematically illustrates yet another arrangement, using thesame reference numerals as the embodiment of FIG. 13, in which theconductor 1308 is arranged in a path directed toward a tip of the lead1300. This may be particularly useful to avoid a lumen (e.g., a styletlumen) that passes through a portion of the lead, but is not present atthe distal end of the lead. In alternative embodiments, separateconductors may be electrically coupled to each electrode and then theseparate conductors are both electrically coupled to another conductorthat passes through the lead body to the proximal end of the lead toprovide for connection to the control unit (for example, an IPG, withindependent controllable, constant-current stimulation channels).

FIG. 19 schematically illustrates yet another embodiment of a lead 1900with, starting from the distal end of the lead, a group of two segmentedelectrodes 1902, two groups of three segmented electrodes 1904 each, andanother group of two segmented electrodes 1906. In this arrangement,each of the electrodes 1902 is ganged with one of the electrodes 1906 asschematically illustrated by the lines 1908 and 1910. It will berecognized that it is also possible to gang more than one of theelectrodes 1902 with one or more of the electrodes 1906 or vice versa.

FIG. 29 schematically illustrates another embodiment of a lead 2900. Inthis instance, there is one circumferential group of two segmentedelectrodes 2902 ganged together and a second circumferential group ofthree segmented electrodes 2904. FIG. 20 schematically illustrates yetanother embodiment of a lead 2000. In this instance, there are fourgroups of three segmented electrodes 2006 each. In the illustratedembodiment, the distal group 2006 (on the left) and the most proximalgroup 2006 (on the right) are ganged together as schematically indicatedby lines 2008, 2010, respectively. It will be understood that in each ofthe embodiments described herein the order of the groups and whichgroup(s) of electrodes are ganged together can be changed to form anypossible arrangement.

Leads can be prepared with only segmented electrodes that are not gangedtogether. FIG. 21 schematically illustrates an embodiment of a lead 2100with four groups of segmented electrodes 2102. Each circumferentialgroup of segmented electrodes includes four electrodes. Thus, the totalnumber of electrodes on lead 2100 is sixteen. FIG. 22 schematicallyillustrates an embodiment of a lead 2200 with three groups of segmentedelectrodes 2202. Each group of segmented electrodes includes fourelectrodes. Thus, the total number of electrodes on lead 2200 is twelve.FIG. 23 schematically illustrates an embodiment of a lead 2300 withthree groups of segmented electrodes 2302. Each group of segmentedelectrodes includes four electrodes. Thus, the total number ofelectrodes on lead 2300 is eight. It will be understood that other leadscan be made with different numbers of groups (e.g., two, three, four,five, six, or more groups) and different numbers of segmented electrodesin each group (e.g., two, three, four, five, six, or more electrodes).It will also be understood that the number of electrodes in eachcircumferential group may be the same or may be different. In someembodiments, the lead does not include a ring electrode. In someembodiments, the lead does not include segmented electrodes that areganged together.

Leads can also include a tip electrode. FIG. 24 schematicallyillustrates one embodiment of a lead 2400 with a tip electrode 2402 andfive groups of segmented electrodes 2404 with three segmented electrodesper group. FIG. 25 schematically illustrates one embodiment of lead 2500with a tip electrode 2502, two groups of segmented electrodes 2504 withthree segmented electrodes per group, and a group of two segmentedelectrodes 2506 that are ganged together as schematically illustrated bythe line 2508. It will be recognized that other arrangements withdiffering numbers of groups and numbers of electrodes in the groups canbe presented. The embodiment of FIG. 25 includes both a tip electrodeand a group of ganged segmented electrodes. It will be recognized that atip electrode can be added to any of the other embodiments disclosedherein.

Leads can also include one or more microelectrodes having a surface areathat is substantially smaller than any single, segmented electrode. FIG.26 schematically illustrates one embodiment of a lead 2600 withmicroelectrode 2602 disposed at a tip of the lead and five groups ofsegmented electrodes 2604 with three segmented electrodes per group.FIG. 27 schematically illustrates one embodiment of lead 2700 with twomicroelectrodes 2702 (the microelectrode with a dotted outline is on theopposite side of the lead) and two groups of segmented electrodes 2704with three segmented electrodes per group. FIG. 28 schematicallyillustrates one embodiment of lead 2800 with two groups of two segmentedelectrodes 2802 that are ganged together, two microelectrodes 2804 (themicroelectrode with a dotted outline is on the opposite side of thelead) with each microelectrode disposed between the two segmentedelectrodes of one of the two groups, and one group of four segmentedelectrodes 2806. It will be recognized that the microelectrodes may bepositioned between the groups of segmented electrodes as illustrated inFIG. 27; between the electrodes of a group of segmented electrodes asillustrated in FIG. 28; proximal to all of the segmented electrodes;distal to all of the segmented electrodes; or any combination thereof(when there is more than one microelectrode). It will be recognized thatone or more microelectrodes can be added to any of the other embodimentsdisclosed herein.

It will also be understood that in all of these embodiments, theelectrodes do not need to be aligned along the longitudinal axis of thelead. The electrodes of one group may be radially staggered with respectto electrodes of one or more of the other groups as shown, for example,in FIG. 2 where the middle groups of segmented electrodes 130 arestaggered and not aligned linearly along the longitudinal axis of thelead 100.

The electrodes can have any suitable size or shape and may be segments,rings, or cylindrical in shape. It will also be understood that theelectrodes can have the same shape or size (or both shape and size) orthat the shape or size (or both shape and size) of the electrodes may bedifferent. The shape(s) of the electrodes may be regular or irregular.It will be recognized that even within a circumferential group thesegmented electrodes may have different shapes or sizes (or bothdifferent shapes and sizes).

The above specification, examples and data provide a description of themanufacture and use of the composition of the invention. Since manyembodiments of the invention can be made without departing from thespirit and scope of the invention, the invention also resides in theclaims hereinafter appended.

What is claimed as new and desired to be protected by United StatesLetters Patent is:
 1. An implantable stimulation lead, comprising: alead body having a longitudinal surface, a proximal end, and a distalend; and a plurality of electrodes disposed along the longitudinalsurface of the lead body near the distal end of the lead body, theplurality of electrodes comprising: a plurality of sets of segmentedelectrodes spaced apart axially along the longitudinal surface of thelead body, each set comprising at least three segmented electrodesdisposed around a circumference of the lead body at a longitudinalposition along the lead body, and a tip electrode disposed at, andcovering, the distal end of the lead body; wherein each of off theplurality of electrodes is configured and arranged to be individuallycoupleable to different stimulation channels of a control module and tobe independently programmable to provide current steering.
 2. The leadof claim 1, wherein each of the sets of segmented electrodes consists ofthree segmented electrodes.
 3. The lead of claim 1, wherein each of thesets of segmented electrodes have a same number of segmented electrodes.4. The lead of claim 3, wherein the plurality of sets comprises a firstset and a second set, wherein the segmented electrodes of the first setare aligned with the segmented electrodes of the second set along thelongitudinal surface of the lead body.
 5. The lead of claim 3, whereinthe plurality of sets comprises a first set and a second set, whereinthe segmented electrodes of the first set are staggered with respect tothe segmented electrodes of the second set along the longitudinalsurface of the lead body.
 6. The lead of claim 1, wherein the lead isconfigured and arranged for implantation in a brain of a human.
 7. Thelead of claim 1, wherein the plurality of sets of segmented electrodescomprises at least three sets of segmented electrodes.
 8. An implantablestimulation system, comprising: the lead of claim 1; and a controlmodule coupleable to the lead.
 9. The implantable stimulation system ofclaim 8, wherein the control module is a constant-current device.
 10. Animplantable stimulation lead, comprising: a lead body having alongitudinal surface, a proximal end and a distal end; and a pluralityof electrodes disposed along the longitudinal surface of the lead bodynear the distal end of the lead body, the plurality of electrodescomprising: a plurality of sets of segmented electrodes spaced apartaxially along the longitudinal surface of the lead body and comprisingfirst and second sets of segmented electrodes, each set comprising atleast three segmented electrodes disposed around a circumference of thelead body at a longitudinal position along the lead body, and a firstring electrode disposed proximal to all of the sets of segmentedelectrodes; wherein each of the plurality of electrodes is configuredand arranged to be individually coupleable to different stimulationchannels of a control module and to be independently programmable toprovide current steering and wherein the first and second sets ofsegmented electrodes have a same number of segmented electrodes.
 11. Thelead of claim 10, wherein the plurality of electrodes further comprisesa second ring electrode disposed distal to all of the sets of segmentedelectrodes.
 12. The lead of claim 10, wherein the plurality of sets ofsegmented electrodes comprises at least three sets of segmentedelectrodes.
 13. The lead of claim 12, wherein the plurality of setsconsists of five sets containing three segmented electrodes each and theplurality of electrodes is arranged in a 3-3-3-3-3-1 arrangement.
 14. Animplantable stimulation system, comprising: the lead of claim 10; and acontrol module coupleable to the lead.
 15. The implantable stimulationsystem of claim 14, wherein the control module is a constant-currentdevice.
 16. An implantable stimulation lead, comprising: a lead bodyhaving a longitudinal surface, a proximal end, and a distal end; and aplurality of electrodes disposed along the longitudinal surface of thelead body near the distal end of the lead body, the plurality ofelectrodes comprising at least four sets of segmented electrodes spacedapart axially along the longitudinal surface of the lead body, each setcomprising at least two segmented electrodes disposed around acircumference of the lead body at a longitudinal position along the leadbody; wherein each of the plurality of electrodes is configured andarranged to be individually coupleable to different stimulation channelsof a control module and to be independently programmable to providecurrent steering.
 17. The implantable stimulation lead of claim 16,wherein the at least four sets of segmented electrodes are arranged in a4-4-4-4 or 2-2-2-2-2-2-2-2 arrangement.
 18. A method for brainstimulation, the method comprising: inserting the lead of claim 1 into abrain of a human; coupling the lead to a control module; and generatingelectrical signals, using the control module, at one or more of theplurality of electrodes to stimulate at least one target neuron of thebrain.
 19. A method for brain stimulation, the method comprising:inserting the lead of claim 10 into a brain of a human; coupling thelead to a control module; and generating electrical signals, using thecontrol module, at one or more of the plurality of electrodes tostimulate at least one target neuron of the brain.
 20. A method forbrain stimulation, the method comprising: inserting the lead of claim 16into a brain of a human; coupling the lead to a control module; andgenerating electrical signals, using the control module, at one or moreof the plurality of electrodes to stimulate at least one target neuronof the brain.